It is often desirable for individuals and small businesses who require only occasional use of a facsimile machine and data modem to share an existing single telephone line between these machines instead of dedicating separate telephone lines to them. In doing so, costs associated with installation and service charges are saved.
A problem with such a shared line arrangement is that an incoming call cannot be identified as either a voice, facsimile machine, or data modem call until the telephone is answered by a person, the facsimile machine, or data modem.
This inability to properly distinguish an incoming call prior to answering can lead to misplaced or unanswered incoming calls. For example, if a facsimile machine answers a voice call, the caller will become confused and possibly believe that a wrong number had been dialed and may hang up. Likewise, if a person answers a facsimile or data modem call, the transmitting device will most likely abort transmission because it did not receive any return "handshake" signals. Important data transmissions can be lost or delayed.
Facsimile machines are currently available with internal delaying circuitry which controls a delay period from the moment an incoming call is detected to when a facsimile machine answers the call. For example, the facsimile machine could answer an incoming call after a predetermined number of telephone rings. Upon answering any incoming call, a facsimile machine will immediately and continuously transmit return handshake signals along the single telephone line. If the incoming call happens to be a facsimile call from a remote facsimile station, the incoming handshake signals would be received by the local facsimile machine and the two machines would connect and begin data transmission.
If, however, the incoming call is a voice call, the facsimile machine would answer the call and begin transmitting return handshake signals for about 40 seconds, After not receiving the appropriate incoming handshake signals from the incoming voice call during this period, the facsimile machine would either disconnect the line or summon a person in the immediate area through the use of a beeper, indicating a voice call. This situation causes inconvenience to the caller because he must listen to the called facsimile station for about 40 seconds before any human is summoned to the telephone. Upon hearing the handshake signals, he will likely hang up.
Furthermore, this type of facsimile machine does not provide for the situation where the incoming call is a data modem call.
U.S. Pat. No. 5,146,489 to Telibasa discloses a device for use with a shared-line telephone/facsimile machine systems. The '489 patent does not provide for a system additionally sharing the telephone line with a data modem.
It is an object of the present invention to provide a method and apparatus which eliminate the need for a dedicated facsimile line and a dedicated data modem line.
It is another object of the invention to allow a person to answer an incoming call, fax, voice, or data modem, while not interfering with or disrupting the handshake procedure if it is a fax or data modem call.
Yet another object of the invention is to accommodate the connection of a separate message machine for allowing incoming callers who do not have automatic-transmission fax machines to call ahead by voice and prepare for fax transmission using on-line decoder detection.
It is another object of the invention to allow the setting of configuration variables for local devices remotely from a touch-tone telephone.
The present invention provides a device and a method for directing incoming calls from a single input telephone line to either a facsimile machine, a data modem, or a telephone. An incoming call is initially assumed to be a voice call, and ample time is provided for allowing a person to answer the phone. The device and method "isolate" both a facsimile machine and a data modem from the telephone until after a predetermined delay period following receipt of a call, thus preventing them from answering the call. The delay period may, for example, be three to seven rings, thus allowing ample time for an operator or answering machine to answer the call, while not causing any serious inconvenience to the caller.
If a person or answering machine has not answered the call within the delay period, an off-hook condition is simulated on the telephone line, thus "answering" the call. The signal on the telephone line is then detected. If the signal includes DTMF tones, various functions are performed including resetting internal variables. If a facsimile handshake signal is detected, the facsimile machine is rung with a ring simulator. The facsimile machine can then read the incoming handshake signal and proceed in a conventional fashion. If, however, neither of these two signals is detected, and a telephone answering device has not answered the call, the data modem port is rung with the ring simulator. The data modem will then begin receiving the transmitted signal in a conventional fashion.
If the call is answered during the delay period provided by the invention and the transmission is a facsimile handshake signal, the call is automatically transferred to the waiting facsimile machine. If a person answers the telephone during the delay period and the call is a data modem transmission, the person must enter certain DTMF digits by pressing the appropriate digits on the touch-tone keypad of the telephone. The call will then be transferred to the data modem.